No problem. It takes a bit of getting used to.
You can attach a photo to your post by going to the bottom of the screen... there is a block labeled "File Attachments". There is a Browse button that you can find the file on your system. When you click "Add Reply" (or post or whatever is on a new Topic), the file will upload.
If you want to insert a pic that's hosted on another site, you need to know the exact URL. Then, click the IMG button above, insert the URL, then click IMG to close the tag.
You can attach only one photo per post. However, you can "insert" from another site more than one.
Hope this helps,
-Rusty